Islanders are going to have to deal with Bruins' Perfection Line much more effectively to win this series

In their first-round playoff victory over the Pittsburgh Penguins, one of the keys for the Islanders was the ability to limit the Penguins’ Sidney Crosby to one goal and one assist in the series and hold the No. 1 line of Crosby, Jake Guentzel and Bryan Rust to four goals and three assists in the six games.

The Bruins’ top line of Brad Marchand, Patrice Bergeron and David Pastrnak produced nearly double that in their team’s first-round win over the Capitals, producing eight goals and five assists in five games.

And in Game 1 of the East Division finals between the Bruins and Islanders on Saturday night in Boston, Boston’s "Perfection Line’’ made it clear they will be a bigger challenge than Crosby and his linemates were.

Pastrnak’s second career playoff hat trick did most of the damage as the Bruins took the opener of the best-of-seven series, 5-2, at TD Garden. Bergeron assisted on two of the goals.

Islanders coach Barry Trotz had said after the morning skate that he believes the Marchand-Bergeron-Pastrnak line is the best in the league.

"They’ve got all the elements,’’ he said. "Bergeron is one of the best two-way centermen, high hockey IQ; Marchie gives them that little energy, but also that physical element, with a high skill level and intelligence, and Pastrnak, to me, is a little more of a pure shooter. As a group, to me, they’re the top line.’’

Pastrnak’s first goal, which tied the score at 1-1 at 19:36 of the first period, came on the power play on the rebound of a shot by David Krejci. His second goal also was a rebound after a shot from Bergeron and gave the Bruins a 2-1 lead at 11:08 of the second.

His third goal, which made it 4-2, came off a turnover at center ice and was aided by Taylor Hall plowing into Islanders defenseman Noah Dobson, moving him out of the way to both screen goalie Ilya Sorokin and open a lane for Pastrnak to score his fifth goal of the postseason. Hall probably could have been called for interference but wasn’t.

Trotz wasn’t happy with the job the Islanders did on the Bruins’ big line in Game 1.

"We’ve got to challenge them a little bit more,’’ he said. "We backed off [and] they’re gonna make plays through you.’’

Against Pittsburgh, the Isles used several different lines against Crosby’s unit, though in the end, it was the second line of center Brock Nelson between wingers Anthony Beauvillier and Josh Bailey, and the top defense pair of Adam Pelech and Ryan Pulock, who matched up most often against Pittsburgh’s top guns.

In Game 1 against Boston, the same five got the assignment against Pastrnak and Co., and it didn’t go as well.

Bergeron had a game-high eight shots on goal, Pastrnak had seven and Marchand had four.

Trotz was asked before the game what the key will be in defending the Bruins’ top unit. "You’ve got to limit their touches,’’ the coach said. "You’ve got to limit their time and space, you’ve got to have layers on the interior, you’ve got to have awareness, you’ve got to have stick detail, you’ve got to have all that.

"You have to limit their options. And you have to do it as a group of five. You can’t do it with just three players; you need all five players. Plus your goaltender is going to have to make some big saves against them.’’

After the game, he said, "We’ve got to tighten up there. We’re gonna need more from our lines. I really felt that I only had really probably one line that was really on top of the game. The other lines had spurts. But we’re gonna have to be, right through our whole lineup, we’re gonna have to do much better.’’

By Colin Stephenson

colin.stephenson@newsday.comColinSNewsday

Colin Stephenson covers the Rangers for Newsday. He has spent more than two decades covering the NHL and just about every sports team in the New York metropolitan area.